it's what we used in TPA-RFC-15 and seems to work.

see team#40363

The idea here is that we don't need to justify every step in the
"actual changes" section. The section will be easier to read that
way. Regrouping this in the lengthy "other alternatives" section will
make the text lighter.

not using clusters make things much more readable.

The rationale here is similar: we list the linux kernel packages and
typically show a bunch of "residual config" packages which we then
manually clean up. That's silly, we should just remove then.

Autoremove is also similar: we're going to cleanup a bunch of stuff
after the upgrade, might as well *not* upgrade those packages in the
first place. This should make the upgrade slightly faster.

We tell people to look for those files but not what to do with
them. That is what we do with them. We clean them up.

That said, clean_conflicts doesn't handle exactly the same file set,
but that's likely to be fixed in the (eventual?) rewrite.